Process of reducing static electricity in polyamide fibers and the like products



PRQCESS F REDUCING STATIC ELECTRICITY IN POLYAMIDE FBERS AND THE .LZKE PROD- UCTS Henry Tiilisch, Kastelsvej 4, Copenhagen, Denmark No Drawing. Filed Sept. 25, 1957, Ser. No. 686,047 Claims priority, application Denmark Sept. 29, 1956 2 Claims. (Cl. 117-106) This invention relates to a process of reducing the tendency of polyamide fibers and molded articles to become electric by friction, i.e. to so-called static eliminators.

In principle the present invention consists in treating polyamide molded bodies and especially polyamide filaments, fibers, ,threads, films, and other products made of polyamides," with an agent containing in its molecule at least one reactive group able to combine with at least one of the reactive groups (=NH and =0) of the polyamides, and containing or forming hydrophilic groups such as -OH and COOH. Only the outer layers of the polyamide products will react with the above mentioned agent, while the inner layers are protected by the outer layers of the relatively long CH -chains of the polyamides, these CH -chains being very resistant to chemical reactions. The inner layers, thus, retain their characteristic properties substantially without any change.

Especially suitable agents according to the present invention are monoor poly-aldehyde with at least two carbon atoms, aldehyde carboxylic acids (aldo acids), hydrins, nitriles, organic or inorganic tanning materials. ,B-propiolactone, and the like compounds such as glyoxal, aldehyde alcohols, like glycol aldehyde, aldo-trioses, aldopentoses, aldo-hexoses, acetaldol, formic acid, glyoxylic acid, glucuronic acid, chlorohydrins, acrylonitrile, tanning materials, such as tannic acid, extracts of oak bark and chromium compounds and the like which are mentioned as examples of such agents which reduce static electricity of polyamide products.

According to the present invention, the polyamide products are treated at a suitable temperature which may range, for instance, from room temperature or even a lower temperature up almost to the melting point of the polyamide concerned depending upon the static eliminator employed and its reactivity. Temperatures between about C. and about 200 C. and preferably between about 80 C. and about 100 C. may be employed. If the temperatureis not toohigh, the filaments, fibers, threads, films, and the like products will not become discolored, but the treatment will require more time than when proceeding at a higher temperature.

The treatment at room temperature must be prolonged, in some cases, up to several days, while, for instance, at 200 C. only a short period of time produces the desired effect.

The polyamide products maybe treated with the agents dissolved and/ or diluted in a suitable solvent and/ or diluent. If the agent, can be evaporated, the polyamide products may preferably be exposed to the vapors of said static ,eliminators. Such a vapor treatment is especially mild and, therefore, does not adversely affect the polyamide.

When carrying out the treatment in a solvent andlor diluent, it is advisable to add a moistening or wetting agent to the liquid, such as pyridine, phosphoric acid, benzyl alcohol, Water soluble aliphatic alcohols, phenols.

.Such moistening or Wetting agents facilitate reaction between the polyamide product and the static eliminator.

According to another embodiment of the present invention the properties of the polyamide products treated according to the present invention are improved considerably by thoroughly washing such treated products in a slightly alkaline solution at elevated temperature above 3,012,905 Patented Dec. 12,, 196-1 40 C., preferably between 70 C. and 100 C. Especially suitable has proved washing with a warm soap solution.

The static eliminating or static reducing e'fiect of the static eliminating agents according to the present invention is frequently enhanced when drying the polyarnide products-possibly after alkaline washing-eta temperature exceeding about 40 C., preferably at a temperature of 70-80" C., or even-if the polyamide product can support it-at temperatures up to the softening point of these products, and exposing the dried products to such a temperature for a prolonged period of time.

Furthermore, it was found that certain static eliminators require an aging treatment in order to develop their advantageous effects. In some instances a satisfactory eifect was achieved by storing the treated material for several weeks while other materials do not require such an aging treatment.

The following examples serve to illustrate the present invention without, however, limiting the same thereto.

EXAMPLE 1 Polyamide filaments are tion containing 5% closed container.

- filaments are washed in distilled water and dried at room temperature. When rubbing the dried filaments between spending untreated material, but

' fingers, no static the fingers, no static electricity is generated at a relative humidity of 58% to (wet bulb method).

7 It may be mentioned here that the method of determining static electricity by rubbing between the fingers the filaments in the untreated or treated state is a very simple and quick method of determining the effectiveness of a static eliminator and is not 'as time consuming as the method of measuring the conductivity of the filament by means of an electrometer. Furthermore, the first mentioned method imitates rather well the rubbing to which fabrics containing polyamide products are exposed in wear. Finally, by the said finger method the treated polyamide cannot only easily be compared with the correalso with e. g.icotton and wool. If the tribe-electrification of the treated *polyamide compares well with the tribo-electrification of cotton or wool, the effect of the treatment may beregarded as satisfactory.

EXAMPLE 2 Polyamide filaments are placed above an aqueous solution containing formic acid at room temperature in a closed container. After a period of 2 days the filaments are washed and dried. When rubbing the dried filaments between the fingers, .no static electricity is generated at a relative humidity 'of 58% to 65%.

EXAMPLE '3 Polyam'ic'le filaments are exposed to the vapors of formic acid generated 'by heating an aqueous 5% formic acid solution at C. for about 20 minutes in a reaction chamber. No static electricity is detected after washing and drying of the treated filaments.

EXAMPLE 4 Polyamide filaments are immersed in an aqueous 5% formic acid solution and are kept therein at room temperature for 4 days. The filaments are then washed and dried. When rubbing the dried filaments between the electricity is generated at a relative v humidity of 58% to 65%.

EXAMPLE 5 Polyamide filaments are immersed in an aqueous 50% formic acid solution and are kept therein at room temperature for 2 days. The treated filaments are washed and dried. When rubbing the dried filaments between the fingers, no static electricity is generated at a relative humidity of 58% to 65%.

EXAMPLE 6 Polyamide filaments are immersed in an aqueous solution containing 5% glyoxal and the solution is heated to 90 C. for 80 minutes. The washed and dried filaments do not show any static electricity.

EXAMPLE 7 Polyamide filaments are exposed at a temperature of 150 C. to the action of vapors of glyoxal produced by heating a 1% glyoxal solution in a reaction chamber immersed in an oil bath and having a reflux condenser, in which the filaments are arranged above said glyoxal solution. After an exposure for 10 minutes the treated filaments are washed and dried. They are free of triboelectrification.

EXAMPLE 8 Polyamide filaments are treated with formic acid as described hereinabove in Examples 1 to 5. The treated filaments are then immersed in an aqueous 1% soap solution and are heated therein to boiling for 4 hours to 16 hours. In most instances, the static eliminating effect of formic acid is improved and the soap-treated filaments can be heated in air at 80 C. for 4 hours without any increase in tribo-electrification.

EXAMPLE 9 Polyamide filaments are treated with glyoxal as described hereinabove in Examples 6 and 7. The treated filaments are heated at 80 C. in an aqueous 1% soap solution for about 6 hours. In many instances the static eliminating effect of the glyoxal treatment is improved.

EXAMPLE l- Polyamide filaments are immersed into an aqueous glucose solution heated to 80 C. for about 4 hours. Substantially complete elimination of static electricity is achieved only by heating the treated filaments in an aqueous 1% soap solution at 80 C. for 4 hours.

EXAMPLE 12 Polyamide filaments are immersed into an aqueous 5% tannic acid solution heated to 80 C. for about 4 hours. Substantially complete elimination of static electricity is achieved by heating the treated filaments in an aqueous 1% soap solution at 80 C. for 4 hours.

EXAMPLE 13 Polyamide filaments are immersed into an aqueous comhours. Substantially complete elimination of static electricity is achieved only by heating the treated filaments in an aqueous 1% soap solution at C. for 4 hours.

EXAMPLE 14 Polyamide filaments are immersed into an aqueous 5% acrylonitrile solution heated to 80 C. for about 4 hours. Substantially complete elimination of static electricity is achieved only by heating the treated filaments in an aqueous 1% soap solution at 80 C. for 4 hours.

EXAMPLE 15 Polyamide filaments are immersed into an aqueous 2% fi-propiolactone solution heated to 80 C. for about 4 hours. Substantially complete elimination of static electricity is achieved only by heating the treated filaments in an aqueous 1% soap solution at 80 C. for 4 hours.

EXAMPLE l6 Polyamide filaments are immersed into a 2% solution of fi-propiolactone in trichloro ethylene and are kept therein for about 10 hours. After drying, the treated filaments show less tribo-electrification than filaments treated with aqueous solutions of B-propiolactone. Substantially complete elimination of static electricity is also achieved by heating the treated filaments in a 1% soap solution at 80 C. for about 4 hours.

EXAMPLE 17 Polyamide filaments are immersed into an aqueous 5% glycol aldehyde solution heated at C., which solution by the addition of ammonia is brought to a pH value of 9, for about 5 hours, whereafter they are washed with distilled water, heated in a 1% soap solution heated at 85 C. for 10 hours, washed with distilled water, heated in the air at 85 C. for 3 hours. The tribe-electricity of the polyamide filaments is essentially reduced.

Similar results are obtained when the glycol aldehyde is replaced by aldo trioze or glucuronic acid.

It has been found that not all the commercially available polyamide fibers can be successfully treated with all the static eliminating agents. A number of such polyamide filaments are more effectively treated, for instance, with formic acid, others with tannic acid, others with ,fi-propiolactone, and so forth. It is, of course, quite easy to determine for each type of polyamide material the most suitable type of static eliminating agent. The following tables show, for instance, the static eliminating effect of various agents on 15 different types of polyamide filaments. The filaments were treated in exactly the same manner with the static eliminating agents, were then heated at 80 C. with 1% soap solution for 4 hours, and dried in air at 80 C. for 4 hours.

A in said table indicates that tribo-electrification is almost completely eliminated, while C indicates complete elimination of tribo-electrification.

No symbol indicates that the static eliminating agent mercial oak bark extract heated to 80 C. for about 4 60 did not act satisfactorily.

- Table I Static eliminating agent 1 2 3 4 6 7 8 9 10 11 12 13 14 15 pH Formic acid A G A A O A A C 9 GlyoxaL. a A o o o 7 3-Ohl0ro-1,2-propane diol A C C A 9 By addition of acetic acid.

5 6 While Table I given hereinabove lists the results the group consisting of hydroxy aldehydes, polyaldehydes, obtained by keeping the filaments in a closed container aldehydo carboxylic acids, hydrins, nitriles, organic tanat room temperature above the solution of the static ning materials, and ,B-propiolactone, at a temperature and eliminating agent for 7 days (formic acid) or by immersfor a period of time sufiicient to substantially reduce ing the filaments into solutions of the static eliminating 5 tribo-electrification of the polyamide product without Subagent at about 80 C. for until 4 hours (the other agents stantially adversely affecting the properties of the treated mentioned in the table), it was found that some of the polyamide product. filaments require higher temperatures, namely up to 2. The process according to claim 1, wherein the poly- 195 C. The following tables illustrate the results obamide product is exposed to the static eliminating comtained at such higher temperatures: 10 pound at a temperature between about room temperature Table II Temp, Static eliminating agent C.. 1 2 3 4 5 6 7 8 9 10 ll 12 13 14 15 of bath Formic acid 140-150 C C C C A A C C A A A C Giyoxal 140-150 A A o A O A A A A o A o Acrylonitrile 125-130 C A A C A C A A C Acetaldol 125-130 A A A A O o A A Table III Temp, Static eliminating agent 0., 1 2 3 4 6 7 s 9 11 12 13 14 15 of bath Formic acid l90l95 A A C A O A Glyoxal C C O O ".1 Aeetaldol a I C A C Glucosemolten- O O O A Acrylonitrile O A C Table IV Temp, Static eliminating agent 0., 1 2 3 4 5 6 7 s 9 10 11 12 13 14 15 of bath 3chloro-1,2-pr0pane diol 125-130 C A C t. A C Same 190-195 C o A A A C Same and ammonia... 180 A A A A A t..- Same and pyridine 190 C C C A C A O C A Table II shows that a treatment of 15 minutes at and about the softening temperature of the poly-amide bathtemperatures of 140-150" C. can give better reproduct. sults than those quoted in Table I. 3. The process according to claim 1, wherein the Table III shows that a bathtemperature of 190195 polyamide product is exposed to the action of a solution C. is too high for some of the filaments, while for of the static eliminating agent. others it can be suitable to use this temperature. 4. The process according to claim 1, wherein the poly- Table IV regards some special experiments with 3- amide product is exposed to the action of vapors of the chloro-l,2-propanediol. The two firstmentioned experistatic eliminating agent. ments show that for a series of filaments this agent gives 5. In a process of reducing static electricity in polygood results with bathtemperatures of 125130 C., 0 amide fibers, films, and the like products, the step which whilst for another series good results are obtained at consists in exposing the polyamide product at room tembathtemperatures of 190-195 C. Only the filaments perature in a closed reaction chamber to the action of 3 and 8 have given good results at both of these bathformic acid vapors for at least two days until tribe-electemperatures. trification of the polyamide is substantially reduced.

In the two lastmentioned experiments of Table IV the 6. In a process of reducing static electricity in polyfilaments have been treated with 3 chloro-1,2 proamide fibers, films, and the like products, the step which panediol to which ammonia or pyridinium bases have consists in immersing the polyamide product at room been added. temperature into an aqueous formic acid solution for at Of course, many changes and variations in the static least two days until tribo-electrification of the polyamide eliminating agents used, in the concentrations in which is substantially reduced. they are employed, in the solvents used for dissolving the 7. In a process of reducing static electricity in polysame, in the manner of application of the agents to the amide fibers, films, and the like products, the step which polyamide material, whether in liquid form or in vapor consists in exposing the polyamide product at about 200 form, in the temperature and duration of the treatment, C. to the action of formic acid vapors for about 20 in the manner in which the treated polyamide material 5 minutes. is further worked up, in the alkaline agents used for im- 8. In a process of reducing static electricity in polyproving the static eliminating action of such agents, and amide fibers, films, and the like products, the step which the like may be made by those skilled in the art in acconsists in immersing the polyamide product at a temperacordance with the principles set forth herein and in the ture of about 90 C. in an aqueous solution of glyoxal claims annexed hereto. for about minutes until tribe-electrification of the I claim: polyamide product is substantially reduced.

1. In a process of reducing static electricity in poly- 9. In a process of reducing static electricity in polyamide fibers, films, and the like molded products, the amide fibers, films, and the like products, the step which step which consists in exposing the polyamide product to consists in exposing the polyamide product at a temperathe action of a static eliminating compound selected from 75 ture of about C; in a closed reaction chamber to the action of glyoxal vapors for about minutes until tribo-electrification of the polyamide product is substantially reduced.

10. In a process of reducing static electricity in polyamide fibers, films, and the like products, the steps which consist in exposing the polyamide product at room temperature in a closed reaction chamber to the action of formic acid vapors for at least two days until triboelectrification of the polyamide is substantially reduced, immersing the treated polyamide product in an aqueous soap solution, heating the soap solution to a temperature of at least 40 C. until no further reduction in triboelectrification is achieved, washing the soap-treated polyamide product with water, and drying the washed polyamide product at a temperature of at least 40 C.

11. In a process of reducing static electricity in polyamide fibers, films, and the like products, the steps which consist in exposing the polyamide product at a temperature of about 150 C. in a closed reaction chamber to the action of glyoxalvapors for about 10 minutes until tribe-electrification of the polyamide product is substantially reduced, immersing the treated polyamide product in an aqueous soap solution, heating the soap solution to a temperature of at least 40 C. until no further reduction in tribo-electrification is achieved, washing the soaptreated polyamide product with water, and drying the washed polyamide product at a temperature of at least C.

12. 'In a process of reducing static electricity in polyamide fibers, films, and the like products, the steps which consist in immersing the polyamide product at about C. into an aqueous tannic acid solution for about 4 hours until tribo-electrification of the polyarnide is substantially reduced, immersing the treated polyamide product in an aqueous soap solution, heating the soap solution to a temperature of at least 40 C. until no further reduction in tribo-electrification is achieved, washing the soaptreated polyamide product with water, and drying the washed polyamide product at a temperature of at least 40 C.

References Cited in the file of this patent UNITED STATES PATENTS 2,317,728 Bristol Apr. 27, 1943 2,343,090 Smith Feb. 29, 1944 2,729,577 Bacon Ian. 3, 1956 2,745,770 Kingerley May 15, 1956 2,808,346 Lutgerhorst Oct. 1, 1957 2,839,431 Rimmer June 17, 1958 

1. IN A PROCESS OF REDUCING STATIC ELECTRICITY IN POLYAMIDE FIBERS, FILMS, AND THE LIKE MOLDED PRODUCTS, THE STEP WHICH CONSISTS IN EXPOSING THE POLYAMIDE PRODUCT TO THE ACTION OF A STATIC ELIMINATING COMPOUND SELECTED FROM THE GROUP CONSISTING OF HYDROXY ALDEHYDES, POLYALDEHYDES, ALDEHYDO CARBOXYLIC ACIDS, HYDRINS, NITRILES, ORGANIC TANNING MATERIALS, AND B-PROPIOLACTONE, AT A TEMPERATURE AND FOR A PERIOD OF TIME SUFFICIENT TO SUBSTANTIALLY REDUCE TRIBO-ELECTRIFICATION OF THE POLYAMIDE PRODUCT WITHOUT SUBSTANTIALLY ADVERSELY AFFECTING THE PROPERTIES OF THE TREATED POLYAMIDE PRODUCT. 